<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no">
    <script src="https://unpkg.com/vue"></script>

    <title>过渡</title>
</head>
<body>

<style rel="stylesheet">
    .fade-enter-active, .fade-leave-active {
        transition: opacity .5s
    }

    .fade-enter, .fade-leave-to {
        opacity: 0
    }
</style>

<div id="demo">
    <button @click="show=!show">toggle</button>

    <transition name="fade">
        <p v-if="show">hello</p>
    </transition>
</div>
<script>

    const demo = new Vue({
        el: "#demo",
        data: {
            show: true
        }
    });

</script>

<style rel="stylesheet">
    .list-item {
        display: inline-block;
        margin-right: 10px;
    }

    .list-enter-active, .list-leave-active {
        transition: all 1s;
    }

    .list-enter, .list-leave-to
        /* .list-leave-active for below version 2.1.8 */
    {
        opacity: 0;
        transform: translateY(30px);
    }
</style>
<div id="list-demo" class="demo">
    <button v-on:click="add">Add</button>
    <button v-on:click="remove">Remove</button>
    <transition-group name="list" tag="p">
    <span v-for="item in items" v-bind:key="item" class="list-item">
      {{ item }}
    </span>
    </transition-group>
</div>
<script>
    new Vue({
        el: '#list-demo',
        data: {
            items: [1, 2, 3, 4, 5, 6, 7, 8, 9],
            nextNum: 10
        },
        methods: {
            randomIndex: function () {
                return Math.floor(Math.random() * this.items.length)
            },
            add: function () {
                let randomNumber = this.randomIndex();
                console.log(randomNumber);
                this.items.splice(randomNumber, 0, this.nextNum++)
            },
            remove: function () {
                this.items.splice(this.randomIndex(), 1)
            },
        }
    })
</script>

</body>
</html>